Durable flame retardant finish for cellulosic materials

ABSTRACT

A composition, for treating a cellulosic material, contains a hydroxyl-functional phosphorus ester containing at least two phosphorus atoms therein, a melamine formaldehyde resin, optionally one or more N-methylol functional resin(s), and a curing catalyst.

BACKGROUND OF THE INVENTION

The present invention relates to flame retardant treatments forcellulose-containing materials, such as cotton and cotton blends (forexample, cotton/Nomex®e cotton/Kevlar®, cotton/nylon-6,cotton/nylon-6,6, cotton/polyester, etc.), which renders such materialsdurable to both laundering and dry cleaning operations.

There are currently several different types of chemical finishes thatcan be applied to cellulosic materials to impart flame retardant (“FR”)properties. Of these systems, only a few create finished fabrics thatcan be laundered and dry-cleaned without losing their FR qualities.These treatments are generally referred to as “durable FR finishes” and,for the most part, can be summed up by referencing two types ofcommercial finishing chemistries: precondensate ammonia cure; andN-methylol functional phosphorus esters. It is surprising that more thanthirty years have passed since these chemistries were first developed,and even more surprising that other technologies have been developed tosupplant their hold on the FR cotton market during that period of time.For persons that have used and/or read about these finishingchemistries, it is understandable why they remain the dominant means forcreating durable FR cotton fabrics. Nevertheless, those same people willalso admit that there are limitations and, in many cases, undesirablefacets to these finishing techniques.

There have been several versions of thetetrakis(hydroxymethyl)-phosphonium chloride (“THPC”) cross-linkingchemistry used over the years, with the precondensate-NH₃ process beingthe most recent of these versions. Although the precondensate-NH₃process may easily be the most durable treatment on the market, thetechnology is far from simple. The application process involves the useof an ammoniation chamber and strict control of application conditionsto obtain consistent results. In addition to demanding applicationconditions, the costs for implementing this technology, licensingexpenses, and the regulatory issues associated with the use of ammoniagas make this technology far from ideal, especially to new arrivals tothe market.

N-methylol functional phosphorus chemistry, although not as durable asthe precondensate-NH₃ chemistry, has also found a wide customer base inthe FR cotton industry due to its ease of application and its use ofcommonly available pad/dry/cure textile finishing equipment. MostN-methylol functional phosphorus chemistry is based on the use ofdimethyl (N-hydroxymethylcarbamoyl-ethyl)phosphonate in conjunction witha melamine formaldehyde (“M-F”) crosslinking resin to enhance its FRperformance, both of which contribute to the emission of significantlevels of formaldehyde during both fabric application and the lifetimeof the treated garments.

The need for the present invention arose from the limitations listedabove, and the desire for alternative FR finishing chemistries andpotential new markets (e.g., furniture upholstery, raised surfacefabrics) that only need an FR treatment to withstand a limited number ofmachine launderings. The main goals of the present invention were todevelop an ER finishing chemistry that would have minimal effect on thephysical characteristics of the treated fabrics (e.g., on strengthretention, hand, dye shade, etc.), would be applicable using thetraditional pad/dry/cure finishing equipment, and would use onlycommonly available commodity chemicals. The outcome of the invention wasthe development of several new FR finishing chemistry embodiments basedon the use of a hydroxyl-functional organophosphorus FR additive incertain durable press (“DP”) finishing formulations containing commonlyavailable components.

SUMMARY OF THE PRESENT INVENTION

The conceptualization and subsequent development of the new FR finishingchemistry based on the use of a hydroxyl-functional organophosphorus FRadditive with commonly available durable press (“DP”) finishing resinshas been validated on full-scale applications equipment in severaltextile mills. The durability of the new FR finishes is believed to bebased on the covalent binding between the FR additive anddimethyloldihydroxyethylene urea (DMDHEU) or melamine-formaldehyde (M-F)and that between cotton cellulose and DMDHEU or M-F. It is accomplishedby using a formulation containing that hydroxyl-functional FR additive,a melamine-formaldehyde resin, optional N-methylol functionalcrosslinking resin(s), and a curing catalyst using common pad/dry/cureapplication equipment. The Figure, which forms a part of the instantspecification, illustrates this novel chemistry.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although the concept of creating a semi-durable (five or lesslaunderings) FR finish from a certain type of hydroxyl-functionalphosphorus-containing ester compound and an N-methylol functional resinis known in the literature (see U.S. Pat. No. 3,746,572, which isincorporated herein in its entirety), previous results were quitelimited in both the finish durability and the flame resistant propertiesof the treated fabrics. At best, these previous systems resulted infabrics that could withstand at most five home launderings. Given thisrestriction and the commercial need for more durable and more flameresistant treatments, commercialization of such an older chemistry wasnever warranted.

An additional example of a flame retardant finishing chemistry similarto that described above is mentioned in PCT Patent Publication No. WO00/29662. Although most of these functional resin systems show littlecommercial potential, the dimethyloldihydroxy-ethylene urea (DMDHEU)flame retardant resin systems are the exception, showing increaseddurability characteristics that may have commercial potential.Nevertheless, even though these systems show higher levels of durabilitythan the previous chemistry described in U.S. Pat. No. 3,746,572, thepractical utility of these new PR systems is limited to low additionlevel application systems such as on highly flammable general wearingapparel that fail to pass a simple 45-degree angle burn test. UsingFR/DMDHEU add-on levels high enough to pass a vertical burn test willresult in unacceptable fabric strength loss percentages equal to andsometimes exceeding 40%. Fabric strength loss percentages above 30% arerarely acceptable in commercial fabrics.

The present invention has improved this general area of chemistry andhas resulted in the development of novel FR finishing systems that canhold up to more than 20-25 home launderings, while satisfying both aminimal strength loss to the fabric construction and the flammabilityrequirements of a vertical burn test. These finishing chemistries arebased on the use of melamine-formaldehyde (“M-F”), by itself or with anadditional N-methylol functional resin (e.g., DMDHEU)), in combinationwith non-volatile hydroxyl-functional phosphorus esters containing ahigh level of phosphorus (for example, a hydroxyl number no more thanabout 300 mg KOH/g and a phosphorus content of no less than about 14 wt%). Examples of these products include the FYROLTEX® HP product and thehigh hydroxyl version of FYROL® PNX, both available from Akzo NobelFunctional Chemicals LLC.

Out of the FR products evaluated during the effort in developing thepresent invention, systems containing the high OH# oligomeric productsFYROLTEX® HP and high hydroxyl version of FYROL® PNX showed efficacy increating durable FR finishes. The FYROL® PNX product (OH#: <5 mg KOH/g),as well as the FYROL® 6 product (OH#: >400 mg KOH/g) both imparted poorFR properties to treated fabrics. As expected, the low hydroxyl productFYROL® PNX did not contain a sufficient quantity of functionality tobond it to the N-methylol functional resins. On the other hand, theFYROL® 6 product (the FR additive discussed in U.S. Pat. No. 3,746,572),which does contain hydroxyl functionality, also failed to provide anadequate FR finish. In the case of the FYROL® 6 product, the compositionactually contained too many reactive groups per phosphorus atom (twohydroxyl groups per molecule and per phosphorus atom), resulting in theconsumption of a large amount of the crosslinking resin with fixation ofonly a small amount of the FR additive onto the fabric substrate. Giventhat the level of the crosslinking resin used drastically affects thephysical properties of the treated fabrics (e.g., strength, hand, etc.),the high levels of resin required for additives like FYROL® 6 makes themcommercially impractical and undesirable. In addition to the aboveproblem and its tendency to yellow fabrics, FYROL® 6 also displayedvolatility problems under fabric curing conditions. Later phosphorusanalysis of cured fabric samples showed a significant portion of the FRadditive had volatilized into the ventilation system of the oven duringapplication.

The results of the above experiments identified non-volatilehydroxyl-functional phosphorus esters containing a high level ofphosphorus, a moderate level of hydroxyl functionality, and a thermaldecomposition/volatilization temperature above 160° C. as the mostdesirable group of FR additives in these finishing systems. Thecombination of these FR product candidates (e.g, FYROLTEX® HP) and M-Fbased binding resin systems (including M-F/DMDHEU combinations) weredeveloped to give a more desirable commercial FR finish over previouslyreported DP-based finishing systems (e.g., as described in U.S. Pat. No.3,746,572 and PCT Patent Publication No. WO 00/29662).

Hydroxy-functional phosphorus ester candidates for use herein conform tothe following formula:

where R₁ is independently selected from alkyl and hydroxyalkyl, R₂ isindependently selected from alkyl, alkoxy, and hydroxyalkoxy, and n isequal to or greater than 1.

In the composition of the present invention, the relative parts byweight of the essential components of the composition can be variedwithin the following exemplary limits: hydroxyl-functional phosphorusester (from about 4 wt % to about 50 wt %), N-methylol functionalresin(s) (from about 2 wt % to about 30 wt %), and a curing catalyst(from about 0.1 wt % to about 15 wt %), with water and other desiredadditives (fabric softener(s), surfactant(s), brightener(s), pH controlagent(s), and the like) also being optionally present. The presentformulation has a preponderant amount of the flame retardant component,as compared to the resin component, further differentiating it from theformulations described in PCT Patent Publication No. WO 00/29662.

Examples illustrating certain experimental work employing the FYROLTEX®HP and high OH# version of FYROL® PNX with the binding resin systems M-Fand DMDHEU/M-F, in accordance with the present invention is given below:

EXAMPLES

1. Binding Resins and Other Chemicals

-   -   FR additives used: FYROLTEX® HP or High OH# FYROL® PNX, which        are hydroxyl functional oligomeric phosphorus ester products        supplied by Akzo Nobel.    -   M-F resins used: ECCOREZ M300 supplied by Eastern Color &        Chemical or AEROTEX® M-3 supplied by Noveon, which are        trifunctional methylated melamine resins.    -   Glyoxal resin used: FREBREZ® 900 supplied by Noveon, an        unbuffered, uncatalyzed DMDHEU resin.    -   Catalysts used: A 70% solution of phosphorous acid (also known        as phosphonic Acid) supplied by Akzo Nobel; Catalyst 531        supplied by Omnova Solutions, a combination of magnesium        chloride and citric acid solution; and Catalyst RD supplied by        Omnova Solutions, ammonium chloride solution.    -   Wetting agent: TERGITOL® TMN-6 supplied by Dow Chemical, an        alcohol ethoxylate surfactant.    -   Softener: CROSSLINK-SS305 supplied by Vulcan Performance        Chemicals, a proprietary reactive silicon softener.        2. Pad-Dry-Cure Equipment Used    -   Pad applicator (laboratory size): an instrument used to apply a        solution to fabric at a specified level (% wet-pickup).    -   Curing oven (laboratory size): an oven that is used to dry and        subsequently to cure the chemically treated fabrics at high        temperatures.    -   Washing machine (household size): used for laundering fabrics        after chemical treatment and curing with AATCC Standard        Detergent 1993.        3. Fabrics    -   100% Cotton scoured and bleached printcloth weighing 108 g/m²        (Testfabrics Style 400).    -   100% Cotton dyed twill weave weighing 246 g/m².    -   50/50 Cotton/Nylon-6,6 dyed blend printed twill weave weighing        254 g/m²    -   35/65 Cotton/Nomex® blend twill weave weighing 192 g/m².        4. Fabric Aftertreatments    -   Washing at 105° F. without the used of a detergent (water wash).    -   Launderings according to AATCC Test Method 124-1996 at 105° F.        with AATCC Standard Detergent 1993 (home laundering        washing/drying —HLWD).        5. Fabric Flammability Testing Methods    -   Limiting Oxygen Index: ASTM D2863-00.    -   Vertical Burn: ASTM D6413-99.        6. Fabric Physical Property Testing Methods    -   Tensile Strength: ASTM D5035-90.    -   Tearing Strength: ASTM D1424-96.        General Application Conditions

The test fabrics were immersed into the desired test solution containingthe FR finish formulation, then fed through a pad applicator to ensurethat both the desired level of chemistry was applied to the fabric andalso that it was applied in a uniform manner. Although it was standardpractice to pad the chemicals on twice using two dips and two nipsduring the laboratory trials, the chemicals were only padded once in thefull-scale mill trials and showed little difference in ultimateperformance. After achieving 9, the desired wet pick-up level, thefabrics were dried and cured. After curing, a short afterwash procedurewas performed at 140° F. to remove any unbound chemicals.

Experimental Results

I. Oligomeric FR Product with a M-F Binding Resin Applied to 100% CottonFabrics 108 G/M² Cotton Twill Treated with FYROLTEX ® HP/M-F HomeLaundering LOI (%)* Before Water Wash 33.0 After Water Wash 31.5  1 HLWDCycle 30.7  5 HLWD Cycles 29.8 10 HLWD Cycles 28.9*Even though there is no pass/fail standard for the LOI measurement,equal to or over 27% is generally considered an acceptable pass/failthreshold for a vertical burn evaluation.Notes:1. Formula: 16.0% FYROLTEX ® HP, 8.0% ECCOREZ ® M3002. The pH of the finish solution was adjusted to 4.0 by addition ofH₃PO₃3. A wet pick-up of 115% was achieved4. Fabric: 100% cotton twill fabric weighing 108 g/m²5. Drying Condition: 180° F. for 3.0 minutes6. Curing Condition: 330° F. for 2.5 minutes

246 G/M² Cotton Twill Treated with FYROLTEX ® HP/M-F Home Laundering LOI(%)* Before Water Wash 33.5 After Water Wash 30.5  1 HLWD Cycle 30.2  5HLWD Cycles 29.0 10 HLWD Cycles 28.0*Even though there is no pass/fail standard for the LOI measurement,equal to or over 27% is generally considered an acceptable pass/failthreshold for a vertical burn evaluation.Notes:1. Formula: 16.0% FYROLTEX ® HP, 8.0% ECCOREZ ® M3002. The pH of the finish solution was adjusted to 4.0 by addition ofH₃PO₃3. A wet pick-up of 75% was achieved4. Fabric: 100% cotton twill fabric weighing 246 g/m²5. Drying Condition: 180° F. for 3.0 minutes6. Curing Condition: 330° F. for 2.5 minutes

An Example is also given to show the performance of the high OH# versionof FYROL® PNX to that of FYROLTEX® HP, where both treatments showadequate FR performance. The lower LOI numbers for the High OH# FYROL®PNX treated fabrics are in part due to the product's lower phosphoruscontent; FYROLTEX® HP has a percent phosphorus of 20.5 wt % and high OH#FYROL® PNX only 15.5 wt %. 246 G/M² Cotton Twill Treated with FYROLTEX ®HB/M-F and High OH# FYROL ® PNX/M-F FR M-F LOI (%)* (%) (%) pH BeforeWater Wash 5 HLWD FYROLTEX ® HP 12 4.0 36.5 34.3 33.1 28% High Hydroxyl12 4.0 31.8 31.5 30.5 FYROL ® PNX*Even though there is no pass/fail standard for the LOI measurement,equal to or over 27% is generally considered an acceptable pass/failthreshold for a vertical burn evaluation.Notes:1. Formula: FR Additive, ECCOREZ ® M3002. The pH of the finish solution was adjusted to 4.0 by addition ofH₃PO₃3. Fabric: 100% cotton twill fabric weighing 246 g/m²4. Drying Condition: 180° F. for 3.0 minutes5. Curing Condition: 330° F. for 2.5 minutesII. Oligomeric FR Product with DMDHEU/M-F Binding Systems Applied to100% Cotton Fabrics

Based on the above observations, work was also completed to evaluatecombination DMDHEU/M-F binding systems that would incorporate the highdurability of the DMDHEU binding systems and the high FR performance andlow strength loss characteristics of the M-F binding systems. The tablesbelow illustrate some of the results: 246 G/M² Cotton Twill Treated withFYROLTEX ® HP/DMDHEU/M-F or FYROLTEX ® HP/M-F Systems Tensile StrengthTear Strength LOI (%)* Fill Retention Fill Retention Warp RetentionFormula 1 HLWD 12 HLWD (kgf) (%) (kgf) Fill (%) (kgf) Warp (%) 1 28.527.3 25.3 69 1.69 73 1.55 70 2 28.3 27.2 30.7 83 2.06 89 1.90 86 3 30.829.5 35.6 96 2.10 91 1.98 90 Control — — 36.9 — 2.32 — 2.21 —*Even though there is no pass/fail standard for the LOI measurement,equal to or over 27% is generally considered an acceptable pass/failthreshold for a vertical burn evaluation.Notes:1. Formula 1: 24% FYROLTEX ® HP, 10.0% FREEREZ ® 900, 1.0% ECCOREZ ®M300, 6.0% Catalyst 531, 4.0% Crosslink-SS305, 0.01% TERGITOL ® TMN-62. Formula 2: 24% FYROLTEX ® HP, 2.0% FREEREZ ® 900, 3.0% ECCOREZ ®M300, 0.20% H₃PO₃, 4.0% Crosslink-SS305, 0.01% TERGITOL ® TMN-63. Formula 3: 24% FYROLTEX ® HP, 7.0% ECCOREZ ® M300, 0.20% H₃PO₃, 4.0%Crosslink-SS305, 0.01% TERGITOL ® TMN-64. A wet pick-up of about 80% was achieved5. Drying Condition: 180° F. for three minutes6. Curing Condition: 330° F. for two minutes

It is apparent from the data above, that as the level of the M-F resinused was increased and the level of DMDHEU resin was decreased, theimproved fabric strength retention properties of the M-F containingsystems was impressive. The FR/DMDHEU systems demonstrated a high levelof effectiveness in binding the FR component to cotton cellulose andexcellent laundering durability. The FR/DMDHEU systems bring with them alevel of fabric strength loss similar to that of normal DP-typefinishing chemistries (about 30-40% strength loss), the major reason forthis is DMDHEU's high capacity to crosslink cotton cellulose. On theother hand, M-F resins are less effective at binding the ER component tocotton cellulose than DMDHEU. As a result, they cause far lesscross-linking in cotton and consequently less strength loss in thetreated fabrics. In addition to lower strength loss, the M-F resinsystems also add an important source of nitrogen to the FR finishingsystem, thereby boosting their initial FR performance over that of theDMDHEU-based systems.

By combining an M-F resin with a DMDHEU resin in the same formulation,the FR finishing system can take advantage of the benefits imparted byboth resin components. The PR/DMDHEU/M-F systems show a high level offlame retardancy after laundering, and at the same time have excellentfabric strength retention properties (80-90%). The DMDHEU resin improvesbinding of the FR component to cotton and the M-F resin enhances theflame retardant properties of the finish through nitrogen/phosphorussynergism, while also minimizing the overall fabric strength loss.

III. Oligomeric Fr Product and a DMDHEU/M-F Binding System Applied toCotton Blend Fabrics (Cotton/Nylon and Cotton/Nones)

In addition to testing the combination FR/M-F/DMDHEU applicationformulations to 100% cotton fabrics, trials were also completed on someexemplary cotton blend fabrics. Two examples (namely, cotton/nylon andcotton/Nomex® blend fabrics) were tested as substrates and the resultsare set forth below: 254 G/M² Cotton/Nylon Blend Twill Treated withFYROLTEX ® HP/DMDHEU/M-F System Home Laundering LOI (%)* Char Length(mm)* Before Water Wash 28.7 70  1 HLWD Cycle 28.5 78  9 HLWD Cycles28.1 75 15 HLWD Cycles 27.5 126*A char length of over 178 is considered passing for the vertical burntest. Even though there is no pass/fail standard for the LOImeasurement, equal to or over 27% is generally considered an acceptablepass/fail threshold for a vertical burn evaluation.Notes:1. Formula: 40.0% FYROLTEX ® HP, 6.0% FREEREZ ® 900, 6.0% AEROTEX ® M-3,0.8% Catalyst RD, 0.02% TERGITOL ® TMN-62. A wet pick-up of 75% was achieved3. Fabric: 50/50 cotton/nylon blend twill fabric weighing 254 g/m²4. Drying Condition: 180° F. for three minutes5. Curing Condition: 330° F. for two minutes

192 G/M² Cotton/NOMEX ® Twill Treated with FYROLTEX ® HP/DMDHEU/M-FSystem Home Laundering LOI (%)* Char Length (mm)* Before Water Wash 37.176  1 HLWD Cycle 35.3 64 12 HLWD Cycles 35.2 74*A char length of over 178 is considered passing for the vertical burntest. Even though there is no pass/fail standard for the LOImeasurement, equal to or over 27% is generally considered an acceptablepass/fail threshold for a vertical burn evaluation.Notes:1. Formula: 20.0% FYROLTEX ® HP, 1.6% FREEREZ ® 900, 2.5% AEROTEX ® M-3,2.0% Catalyst 531, 0.02% TERGITOL ® TMN-62. A wet pick-up of 89% was achieved3. Fabric: 35/65 cotton/NOMEX ® blend twill fabric weighing 192 g/m²4. Drying Condition: 180° F. for 3.0 minutes5. Curing Condition: 330° F. for 2.0 minutes

Depending on the FR properties, durability requirements, and fabricstrength properties (e.g., tensile and tear strength retention) desiredfor a target end-use application, an appropriate FR/DMDHEU/M-F or FR/M-Fsystem can be formulated to meet those needs.

The foregoing Examples are presented merely to illustrate certainembodiments of the present invention and should not be construed in alimiting sense for that reason. The scope of protection sought is setforth in the claims that follow.

1. A composition, for treating a cellulosic material, which comprises ahydroxyl-functional phosphorus ester containing at least two phosphorusatoms therein, a melamine-formaldehyde resin, optionally one or moreN-methylol functional resin(s), a curing catalyst.
 2. A composition asclaimed in claim 1 wherein the curing catalyst is an ammonium salt.
 3. Acomposition as claimed in claim 1 wherein the curing catalyst comprisesa mixture of a Lewis acid catalyst and a carboxylic acid.
 4. Acomposition as claimed in claim 3 wherein the carboxylic acid is citricacid.
 5. A composition as claimed in claim 3 wherein the Lewis acidcatalyst is magnesium dichloride.
 6. A composition as claimed in claim 1wherein the curing catalyst is selected from the group consisting ofphosphorus acid and phosphoric acid.
 7. A composition as claimed inclaim 1 wherein the hydroxyl-functional phosphorus ester is selectedfrom the group consisting of a mixed phosphate/phosphonate ester of CASNo. 70715-06-09 and a phosphate ester formed by reactingtriethyl-phosphate, phosphorus pentoxide, ethylene glycol and ethyleneoxide.
 8. A composition as claimed in claim 1 wherein thehydroxyl-functional phosphorus ester is a mixed phosphate/phosphonateester.
 9. A composition as claimed in claim 1 wherein thehydroxyl-functional phosphorus ester is a polyphosphate.
 10. Acomposition as claimed in claim 1 wherein the hydroxyl-functionalphosphorus ester is a polyphosphonate.
 11. A composition as claimed inclaim 1 wherein the composition contains DMDHEU as the N-methylolfunctional resin.
 12. A composition as claimed in claim 1 wherein thecuring catalyst is an ammonium chloride solution, thehydroxyl-functional phosphorus ester is selected from the groupconsisting of a mixed phosphate/phosphonate ester of CAS No. 70715-06-9and a phosphate ester formed by reacting triethyl phosphate, phosphoruspentoxide, ethylene glycol and ethylene oxide, and the compositioncontains DMDHEU as the N-methylol functional resin.
 13. A composition asclaimed in claim 1 wherein the curing catalyst comprises a mixture ofmagnesium dichloride and citric acid, the hydroxyl-functional phosphorusester is selected from the group consisting of a mixedphosphate/phosphonate ester of CAS No. 70715-06-9 and a phosphate esterformed by reacting triethyl phosphate, phosphorus pentoxide, ethyleneglycol and ethylene oxide, and the composition contains DMDHEU as theN-methylol functional resin.
 14. A composition as claimed in claim 1wherein the curing catalyst is phosphorous acid, the hydroxyl-functionalphosphorus ester is selected from the group consisting of a mixedphosphate/phosphonate ester of CAS No. 70715-06-9 and a phosphate esterformed by reacting triethyl phosphate, phosphorus pentoxide, ethyleneglycol and ethylene oxide and the composition contains DMDHEU as theN-methylol functional resin.
 15. A composition as claimed in claim 1wherein the hydroxyl-functional phosphorus ester conforms to thefollowing formula:

where R₁ is independently selected from alkyl and hydroxyalkyl, R₂ isindependently selected from alkyl, alkoxy, and hydroxyalkoxy, and n isequal to or greater than
 1. 16. A fabric that has been treated with thecomposition of claim
 1. 17. A composition as claimed in claim 2 whereinthe hydroxyl-functional phosphorus ester conforms to the followingformula:

where R₁ is independently selected from alkyl and hydroxyalkyl, R₂ isindependently selected from alkyl, alkoxy, and hydroxyalkoxy, and n isequal to or greater than
 1. 18. A composition as claimed in claim 3wherein the hydroxyl-functional phosphorus ester conforms to thefollowing formula:

where R₁ is independently selected from alkyl and hydroxyalkyl, R₂ isindependently selected from alkyl, alkoxy, and hydroxyalkoxy, and n isequal to or greater than
 1. 19. A composition as claimed in claim 4wherein the hydroxyl-functional phosphorus ester conforms to thefollowing formula:

where R₁ is independently selected from alkyl and hydroxyalkyl, R₂ isindependently selected from alkyl, alkoxy, and hydroxyalkoxy, and n isequal to or greater than
 1. 20. A composition as claimed in claim 5wherein the hydroxyl-functional phosphorus ester conforms to thefollowing formula:

where R₁ is independently selected from alkyl and hydroxyalkyl, R₂ isindependently selected from alkyl, alkoxy, and hydroxyalkoxy, and n isequal to or greater than 1.